(1) Field of the Invention
The present invention relates to an electronic conference system for conducting a remote conference among a plurality of offices, and more particularly, to a remote conference system employing electronic board units, in which the supervision, update and control of picture data are improved.
(2) Description of the Prior Art
In recent years, as a device to allow a conference between conference members remote from each other, an electronic board unit has been developed as an alternative to a conference telephone or a conference integrated television/telephone system.
The conference telephone or the conference integrated television/telephone system achieve their object of enabling a remote conference to be held. However, the conference telephone system can transmit only audio signals and, therefore, has a disadvantage in that it cannot supply the conference members with sketches or other handwritten material during the conference. On the other hand, the conference integrated television/telephone system can pick up handwritten materials and transmit them in the form of visual signals, i.e., pictures, greatly assisting the members of a remote conference. However, to transmit the picked up hand-written materials, the transmission line must have a wide bandwidth. Also, the television camera viewing area at the transmission side that can be picked and transmitted up is relatively small. Therefore, the conference integrated television/telephone system has a disadvantage in that it is difficult to transmit materials written on a wide board. Thus, an electronic board unit, which can transmit the data for material handwritten on a board having a wide area and display the transmitted pictures at a receiving station, has been provided
In an electronic conference system employing the electronic board units, material is handwritten, by means of, for example, a felt pen or a marker pen, on an input board, e.g., a tablet or a digitizer, so that the handwritten input data is input and stored at one station or office (hereinafter referred to as a station). The handwritten input data is transferred through a telephone line to a remote station and the received pictures are displayed there on a display unit such as a CRT monitor or a projector. Since the handwritten input data can be transmitted along with audio signals, the use of an electronic board unit is of great assistance to the members of a remote conference.
In the electronic conference system employing the electronic board units, by including color data in the handwritten input data, color pictures also can be displayed on a color picture display unit. In addition, the displayed materials can be recorded as hard copies.
Generally, in a remote conference, the members of the conference each use respective picture display units, during the conference for displaying pictures, which receive picture data from respective storage units (for example, floppy disks). In this case, it is often necessary, in view of the object of the conference, to display the same picture simultaneously on all of the picture display units. The picture data for constructing such a picture is usually previously formed by a member of the conference, and is recorded in the storage unit at his or her station. The picture data is also transferred through transmission lines to the respective picture display units and recorded in their respective storage units. During a conference, it is desired that, when one of the members of the conference designates a common picture number for the picture being displayed on the picture display unit, the same picture can be displayed at the other respective picture display units. When a correction is added to previously formed and/or recorded picture data, a new picture number must be provided and registered. In this situation, it would be desireable to record (duplicate) the same picture data in respective storage units in a plurality of offices remote from each other, and to provide a picture number (an absolute number) common to the respective picture display units to the same picture data. However, such an electronic conference system for use in this case is not known.
In a conventional electronic conference system employing electronic board units, picture data of a picture written at a first station is provided with a picture number which can only be used in that first station. When the picture data formed at the first station is transferred to a second station and stored in the storage unit in the second station, the picture data is, conventionally, provided with another picture number, usually different from the picture number provided at the first station. Therefore, the same picture data has different picture numbers at each respective station. Accordingly, it is difficult to simultaneously display the same picture at different stations. To simultaneously display the same picture at different stations, the picture data of the picture being displayed at the first station is transferred to the other stations. This, however, requires transmission lines with a high transmission capacity or otherwise limits the transmission speed and, as a consequence, the display speed.
Even if a common absolute number is assigned to the same picture data stored in individual storage units of the stations remote from each other, so that the same picture data is commonly controlled in each respective station, a further disadvantage occurs when an addition or a correction is made to an existing picture data which has been numbered with a common absolute number. That is, in this case, the added or corrected picture data has an absolute number different from that of the original picture data. Therefore, when the added and corrected part of the picture data is to be transmitted to a remote station, the entire set of picture data must be transmitted even when the added and corrected part is very small.
This also causes a requirement for transmission lines with a high transmission capacity or again limits the transmission speed.
Further, even when the same picture can be simultaneously displayed at different stations, it is often necessary for a different picture to be displayed at one of the stations.